Primary exercises
- Manually created factor.
In a study participants were asked whether their sport activity is
none, oncePerWeek, severalPerWeek
or daily.
Build a proper factor for the responses below and store it in a variable
w.
Print the factor.
Write the code to count the numbers of occurrences of each level and
print the counts.
severalPerWeek, none, none, oncePerWeek, oncePerWeek, oncePerWeek, oncePerWeek, ?, none, none
v <- c( "severalPerWeek", "none", "none", "oncePerWeek", "oncePerWeek", "oncePerWeek", "oncePerWeek", NA, "none", "none" )
w <- factor( v, levels = c( "none", "oncePerWeek", "severalPerWeek", "daily" ) )
w
[1] severalPerWeek none none oncePerWeek oncePerWeek oncePerWeek oncePerWeek <NA> none none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 5 × 2
f n
<fct> <int>
1 none 4
2 oncePerWeek 4
3 severalPerWeek 1
4 daily 0
5 <NA> 1
- A factor with a random content.
Read help about the function sample.
Then study and try the following lines of code to understand the
results.
Next, understand why an error is generated and use replace
argument to generate a vector with 100 samples.
Store this vector in a variable v and build a factor
w from it.
Finally, count the numbers of occurrences of each level in
w.
Ensure, that levels are in order provided in the variable
lvs.
lvs <- c( "none", "oncePerWeek", "severalPerWeek", "daily" )
sample( lvs, 3 )
[1] "severalPerWeek" "none" "oncePerWeek"
sample( lvs, 3 )
[1] "severalPerWeek" "daily" "oncePerWeek"
sample( lvs, 3 )
[1] "daily" "severalPerWeek" "oncePerWeek"
sample( lvs, 100 )
Error in sample.int(length(x), size, replace, prob): cannot take a sample larger than the population when 'replace = FALSE'
v <- sample( lvs, 100, replace = TRUE )
w <- factor( v, levels = lvs )
w
[1] oncePerWeek oncePerWeek daily daily severalPerWeek none daily none daily oncePerWeek
[11] none oncePerWeek none daily none severalPerWeek oncePerWeek daily none daily
[21] oncePerWeek none oncePerWeek daily none daily none none severalPerWeek severalPerWeek
[31] daily none none severalPerWeek daily severalPerWeek none severalPerWeek none none
[41] oncePerWeek daily oncePerWeek none none daily oncePerWeek daily severalPerWeek none
[51] daily severalPerWeek oncePerWeek oncePerWeek none severalPerWeek daily none severalPerWeek oncePerWeek
[61] oncePerWeek daily severalPerWeek severalPerWeek daily oncePerWeek oncePerWeek oncePerWeek oncePerWeek none
[71] daily daily daily oncePerWeek daily oncePerWeek severalPerWeek daily severalPerWeek severalPerWeek
[81] oncePerWeek daily oncePerWeek oncePerWeek oncePerWeek oncePerWeek severalPerWeek none none daily
[91] daily severalPerWeek oncePerWeek none severalPerWeek none severalPerWeek severalPerWeek oncePerWeek oncePerWeek
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 4 × 2
f n
<fct> <int>
1 none 25
2 oncePerWeek 28
3 severalPerWeek 21
4 daily 26
- Reordering factor levels.
When a factor is shown on an axis of a plot, the order is given by its
levels.
The factor w from the previous exercise will be then shown
in this order: none, oncePerWeek,
severalPerWeek, daily.
But for a picture in a manuscript the following order might be needed:
daily, severalPerWeek,
oncePerWeek, none.
Apply to w one of the fct_ functions from the
tidyverse library to produce a factor w2 with
the requested order.
Show the levels of w2.
Again show the number of elements of each level in w2 and
compare it with the table of the previous exercise.
w2 <- fct_relevel( w, c( "daily", "severalPerWeek", "oncePerWeek", "none" ) )
levels( w2 )
[1] "daily" "severalPerWeek" "oncePerWeek" "none"
fct_count( w2 )
# A tibble: 4 × 2
f n
<fct> <int>
1 daily 26
2 severalPerWeek 21
3 oncePerWeek 28
4 none 25